Magnitude of the greater of 2 resistors?

[Bearbull24.5]

Homework Statement

A 20 V emf is placed across 2 resistors in a series, a current of 2 A is present in each of the resistors. When the same emf is placed across the same 2 resistors in parallel, the current through the emf is 10 A. What is the magnitude of the greater of the 2 resistances?

Homework Equations

Series- I=I1=I2
delta V=I1R1+I2R2
Parallel- I=I1+I2

The Attempt at a Solution

I attempted to use the delta V equation, slightly off in my answer

 

[Delphi51]

There is no way to tell if you made a little mistake - you haven't shown your work.

 

[Bearbull24.5]

This was a question from a previous test and the work I have down is scrambled and makes little sense. Those were the equations I could pick out and I'm not even sure if I came up with my answer by working it through or I just picked an answer.

 

[berkeman]

Homework Statement

A 20 V emf is placed across 2 resistors in a series, a current of 2 A is present in each of the resistors. When the same emf is placed across the same 2 resistors in parallel, the current through the emf is 10 A. What is the magnitude of the greater of the 2 resistances?

Homework Equations

Series- I=I1=I2
delta V=I1R1+I2R2
Parallel- I=I1+I2

The Attempt at a Solution

I attempted to use the delta V equation, slightly off in my answer

I don't know what a delta-V equation is.

Just write the two equations for the two cases given. You end up with two equations and two unknowns (R1 and R2). Solve for R2, and you get a quadratic equation. Solve the quadratic equation, and plug that back into the first equation to get R1.

Could you please show us work along the lines of what I've outlined for you?